CN201593993U - Trace gas flowmeter for testing permeability of low-permeability rock - Google Patents

Abstract

A trace gas flowmeter for testing the permeability of low-permeability rock is applied to testing the gas permeability of stratum rock. The device mainly comprises an intercepting pipe, a communicating pipe, an air inlet pipe and a U-shaped transparent pipe, wherein one end of the U-shaped transparent pipe is connected with the communicating pipe, and the U-shaped transparent pipe is communicated with the communicating pipe. The other end of the communicating pipe is fixed with a cut-off pipe. The middle part of the communicating pipe is connected with an air inlet pipe which is communicated with the communicating pipe. The effect is as follows: the instantaneous gas flow of the rock sample of the low-permeability reservoir can be tested. And the testing requirement of the rock sample of the low-permeability reservoir is met. By the trial of the micro gas flowmeter, the environmental, system and human errors are reduced, the measurement result is accurate, the repeatability is good, and the working efficiency is improved.

Description

Trace Gas Flow Meter for Testing Low Permeability Rock Permeability

technical field

The utility model relates to petroleum exploration and development technology, in particular to a device for testing the gas permeability of formation rocks in a laboratory, which is a flow metering device for measuring the instantaneous flow of gas passing through rocks.

Background technique

When testing rock gas permeability, it is necessary to measure the gas flow through the rock sample. Trace gas flowmeters are particularly important in the gas permeability test of low-permeability rock samples. Trace gas flowmeters affect the gas permeability test results and play a decisive role in measuring the gas permeability of low-permeability samples. At present, the soap film flowmeter is a classic gas measuring device used at home and abroad to test the gas permeability of rocks. It can push the flow rate of the bubble film in different pipe diameters through the gas and convert it into the flow rate per unit time. The disadvantages of the soap film flowmeter are: (1) There are many materials to prepare, and flow tubes with different diameters need to be replaced for rock samples with different permeability; (2) The test procedure is complicated; (3) The sample test is labor-intensive.

Rock gas permeability can also be tested using a mass flow meter. The mass flow meter has a high degree of automation, but it still has its shortcomings: (1) The external environment affects the measurement results, such as the accurate measurement results can only be obtained when the voltage is stable; (2) The stability of the electronic components has a great influence on the flow measurement. Accuracy has a big impact, especially in low flow tests. (3) The minimum measurement accuracy of mass flowmeters currently on the market is 10ml/min. When testing low-permeability rock samples, the accuracy of the flowmeter is required to be below 1ml/min, and the mass flowmeter cannot meet the test requirements for low-permeability rock samples.

Utility model content

The purpose of the utility model is to provide a trace gas flowmeter for testing the permeability of low-permeable rocks. When gases with different flow rates enter the trace gas flowmeter, a certain water level difference will be generated in the liquid at both ends of the U-shaped transparent tube. The water level difference at both ends of the U-shaped transparent tube is converted to obtain the instantaneous flow rate of the gas. Solve the problems of low measurement accuracy and low work efficiency in the conventional gas permeability test of low-permeability reservoir rock samples, meet the needs of low-permeability reservoir rock sample testing, reduce labor intensity, and improve work efficiency.

The technical solution adopted by the utility model is: a trace gas flowmeter for testing low-permeability rock permeability, which is mainly composed of a shut-off pipe, a communication pipe, an air intake pipe and a U-shaped transparent pipe, and is characterized in that: one end of the U-shaped transparent pipe is connected to There is a Unicom pipe, and the U-shaped transparent pipe is connected with the Unicom pipe. A shut-off tube is fixed in the other end of the communication tube. An air intake pipe is connected to the middle part of the communication pipe, and the air intake pipe communicates with the communication pipe. When the trace gas in the test process enters the connecting pipe through the intake pipe, the gas is subjected to certain resistance when passing through the intercepting pipe, which will generate a certain pressure in the connecting pipe and cause the liquid level at both ends of the U-shaped transparent pipe to change. According to the principle that a certain pressure value corresponds to a certain flow rate, and different pressures correspond to different flow rates, observe the change of the liquid level at both ends of the U-shaped transparent tube. After the micro gas flowmeter is calibrated, it can measure the functional relational expression of gas permeability, flow rate and water level reading of rock samples under different pressures, and obtain different flow rates corresponding to different water level readings.

The diameter of the U-shaped transparent tube is between 4 and 8 millimeters; the height of the U-shaped transparent tube is between 750 and 950 millimeters. There are scales at both ends of the U-shaped transparent tube.

By changing the diameter of the cut-off tube, the flow of trace gas can be controlled. The inner diameter of the shut-off tube is between 0.02 and 0.1 mm.

Beneficial effects of the utility model: the utility model is a trace gas flowmeter for testing the permeability of low-permeability rocks, which can test the gas instantaneous flow rate of low-permeability reservoir rock samples. Meet the testing needs of low-permeability reservoir rock samples. Through the trial of the micro gas flowmeter, the environment, system and human errors are reduced, the measurement results are accurate, the repeatability is good, the labor intensity of the test is reduced, and the work efficiency is improved.

Description of drawings

Figure 1 is a schematic cross-sectional view of the structure of a trace gas flowmeter for testing the permeability of low-permeability rocks according to the present invention.

In the figure, 1. shut-off pipe, 2. Unicom pipe, 3. intake pipe, 4. U-shaped transparent pipe.

Detailed ways

Embodiment 1: Taking a trace gas flowmeter for testing low-permeability rock permeability as an example, the utility model is further described in detail.

See Figure 1. The utility model is a trace gas flowmeter for testing the permeability of low-permeable rocks. Unicom pipe 2, U-shaped transparent pipe 4 and Unicom pipe 2 Unicom. A cut-off pipe 1 is fixed in the other end of the communication pipe 2 . The diameter of the shut-off tube 1 is 0.05 mm. An air intake pipe 3 is connected to the middle part of the communication pipe 2, and the air intake pipe 3 communicates with the communication pipe 2.

The diameter of the U-shaped transparent tube 4 is 5 mm; the height of the U-shaped transparent tube 4 is 800 mm, and the two ends of the U-shaped transparent tube 4 have a scale of 800 mm liquid column height respectively.

Trace gas flowmeter is particularly important in the gas permeability test of low-permeability samples. It not only affects the accuracy of gas permeability results, but also plays a decisive factor in whether low-permeability and ultra-low-permeability samples can be measured. From the following formula, we can It can be seen that, except for the gas flow rate, other parameters affecting the gas permeability can be measured with legal measuring instruments. The development of micro gas flowmeter makes up for the defect that soap film flowmeter and mass flowmeter cannot adapt to the minimum flow rate. The minimum flow rate of the trace gas flowmeter for testing the permeability of low-permeability rocks can reach 0.00375ml/s.

K _a = (2×Q _o ×P _a ×μ×L)/A×(P ₁ ² -P ₂ ² )

_Ka - air permeability, mD;

Q _o - gas flow rate, ml/s

P _a - atmospheric pressure, MPa;

μ-gas viscosity, mPa.s;

L-sample length, cm;

A-sample end area, cm ² ;

P ₁ , P ₂ --- Absolute pressure at the inlet and outlet respectively (rounded to two decimal places), MPa;

The gas obtained in the experiment is connected to the inlet of the inlet pipe 3 of the micro gas flowmeter for testing the permeability of the low-permeability rock; Due to the effect of the shut-off tube 1, a certain pressure will be generated when the gas passes through, so that a certain water level difference will be generated on the U-shaped transparent tube 4. Through the calibration of the standard instrument, a certain water level difference corresponds to a certain flow rate. When the pressure is stable, the flow of gas through the sample is also stable, so that the flow of gas through the sample can be measured.

Comparison of flow rate per unit pressure of various flowmeters

It can be seen from the above table that compared with the soap film flowmeter, the micro gas flowmeter developed has high precision, simple operation, and is not affected by the error caused by timing; The gas flowmeter has good stability and small fluctuations.

Claims (3)

1. A trace gas flowmeter for testing the permeability of low-permeable rocks, mainly composed of shut-off pipe (1), communication pipe (2), air inlet pipe (3) and U-shaped transparent pipe (4); it is characterized in that: One end of the U-shaped transparent tube (4) is connected with a Unicom tube (2), the U-shaped transparent tube (4) communicates with the Unicom tube (2), and a shut-off tube (1) is fixed in the other end of the Unicom tube (2), An air intake pipe (3) is connected to the middle part of the communication pipe (2), and the air intake pipe (3) communicates with the communication pipe (2). 2. The micro gas flowmeter for testing low-permeability rock permeability according to claim 1, characterized in that: the diameter of the U-shaped transparent tube (4) is between 4 and 8 millimeters; the diameter of the U-shaped transparent tube (4) The height is between 750-950 millimeters, and the two ends of the U-shaped transparent tube (4) have scales respectively. 3. The micro-gas flowmeter for testing the permeability of low-permeability rocks according to claim 1, characterized in that: the inner diameter of the shut-off tube (1) is between 0.02-0.1 mm.